-Wall -Werror

we can't even be here if the fd is not valid

Makefile

@@ -1,5 +1,6 @@
 default: luad luac
 
+CFLAGS=-Wall -Werror
 luad: LOADLIBES=-llua
 
 install:

luad.c

@@ -19,16 +19,29 @@
 #include <poll.h>
 #include <arpa/inet.h>
 
+#include <stdarg.h>
+#include <stdnoreturn.h>
 
 static int sigchild_fd = -1;
 
 static void handle_sigchld(int num) {
     if(sigchild_fd >= 0) {
-        write(sigchild_fd, "\n", 1);
+        (void) !write(sigchild_fd, "\n", 1);
     }
 }
 
-#define die(...) error(EXIT_FAILURE, errno, __VA_ARGS__)
+static void noreturn die(char *fmt, ...) {
+    va_list ap;
+    va_start(ap, fmt);
+    if(errno > 0) {
+        fprintf(stderr, "luad: %s: ", strerror(errno));
+    } else {
+        fprintf(stderr, "luad: ");
+    }
+    vfprintf(stderr, fmt, ap);
+    exit(1);
+}
+
 
 int open_socket(char * pathname) {
     struct sockaddr_un addr;
@@ -66,7 +79,7 @@ int * fds_from_msg(struct msghdr *msg, int * peer_fds) {
         if(cmsg->cmsg_level == SOL_SOCKET &&
            cmsg->cmsg_type == SCM_RIGHTS) {
             int passed_fd_count = (cmsg->cmsg_len - CMSG_LEN(0)) / sizeof (int);
-            if(i <= 3) {
+            if(i + passed_fd_count <= 3) {
                 memcpy(&peer_fds[i], CMSG_DATA(cmsg), passed_fd_count * sizeof(int));
 
             } else {
@@ -94,7 +107,7 @@ int * fds_from_msg(struct msghdr *msg, int * peer_fds) {
     }
 }
 
-int start_lua_child(lua_State *L,
+void start_lua_child(lua_State *L,
                      char * command_line, int command_line_length,
                      int * fds) {
     char * word = command_line;
@@ -104,7 +117,7 @@ int start_lua_child(lua_State *L,
 
     fflush(stdout); fflush(stderr);
     for(int i=0; i < 3; i++) {
-        if(fds[i] > 0) dup2(fds[i], i);
+        dup2(fds[i], i);
     }
 
     lua_newtable(L);            /* arg */
@@ -118,12 +131,13 @@ int start_lua_child(lua_State *L,
         lua_seti(L, -2, i++);
         word = word_end + 1;
     }
+    if(! pathname) {
+        die("no script name received from client");
+    }
     lua_setglobal(L, "arg");
     int status = luaL_dofile(L, pathname);
     if (status) {
         die("Lua error: %s", lua_tostring(L, -1));
-    } else {
-        return 0;
     }
 }
 
@@ -132,8 +146,8 @@ pid_t fork_lua(lua_State *L,
                int * fds) {
     pid_t pid = fork();
     if(pid == 0) {
-        exit(start_lua_child(L, command_line, command_line_length,
-                             fds));
+        start_lua_child(L, command_line, command_line_length, fds);
+        exit(0);
     } else if(pid > 0) {
         free(command_line);
         return pid;
@@ -148,12 +162,10 @@ struct peer_entry {
     struct sockaddr_un addr;
 } peer_entries[500];
 
-
 bool register_peer(pid_t pid, struct sockaddr_un *addr, int addrlen) {
     if(addrlen > sizeof (struct sockaddr_un))
         return false;
 
-    struct peer_entry *p = peer_entries;
     int peer_entries_max = sizeof peer_entries / sizeof(peer_entries[0]);
 
     for(int i=0; i < peer_entries_max; i++) {
@@ -208,7 +220,7 @@ int main(int argc, char **argv)
 
     int socket = open_socket(socket_path);
     struct sockaddr_un peer_addr;
-    socklen_t peer_addr_len;
+
     char buf[1025];
     struct iovec iov[1];
     iov[0].iov_base = buf;
@@ -244,6 +256,8 @@ int main(int argc, char **argv)
         if(pollfds[0].revents) {
             if(find_peer(0)) {
                 int len = recvmsg(socket, &msg , 0);
+                if(len<=0) continue;
+
                 int peer_fds[3];
                 if(fds_from_msg(&msg, peer_fds)) {
                     char *argline = malloc(len);
@@ -253,9 +267,8 @@ int main(int argc, char **argv)
                     memmove(argline, buf, len);
 
                     pid_t child_pid = fork_lua(L, argline, len, peer_fds);
-                    if(child_pid >= 0) {
-                        register_peer(child_pid, &peer_addr, msg.msg_namelen);
-                    }
+                    register_peer(child_pid, &peer_addr, msg.msg_namelen);
+
                     /* close peer fds in parent */
                     close(peer_fds[0]);
                     close(peer_fds[1]);
@@ -268,8 +281,10 @@ int main(int argc, char **argv)
             pid_t pid;
             int wstatus;
 
-            read(pollfds[1].fd, buf, sizeof buf);
-            while((pid=waitpid(0, &wstatus, WNOHANG)) > 0) {
+            if(read(pollfds[1].fd, buf, sizeof buf) < 0)
+                continue;
+
+            while((pid = waitpid(0, &wstatus, WNOHANG)) > 0) {
                 struct peer_entry *peer = find_peer(pid);
                 if(peer) {
                     uint32_t ret = 0;